Detection of the arrival of material at a point in a rolling mill



Sept. 15, 1964 J. HARLEY ETAL 3,143,563

DETECTION OF THE ARRIVAL OF MATERIAL AT A POINT IN A ROLLING MILL Filed June 6, 1960 5 Sheets-Sheet l voT Isa/5F:

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DETECTION OF THE ARRIVAL 0F MATERIAL AT 7 A POINT IN A ROLLING MILL Filed June 6, 1960 5 Sheets-Sheet 2 m A k n OSCILLATOR INVENTORS John Hurley Jakob Zuweis ATTORNEYS J. HARLEY ETAL DETECTION OF THE ARRIVAL OF MATERIAL AT Sept. 15, 1964 3,148,563

A POINT IN A ROLLING MILL 5 Sheets-Sheet 3 Filed June 6, 1960 M m 5 E L v L E m R A 2 IRS w. NM I. H #K 3 mm Sept. 15, 1964 J. HARLEY ETAL DETECTION OF THE ARRIVAL OF MATERIAL AT A POINT IN A ROLLING MILL 5 Sheets-Sheet 4 Filed June 6, 1960 l/VVE/VTURS JON/V HARLEY M ;m ma

Sept. 15, 1964 J. HARLEY ETAL 3,148,563

DETECTION OF THE ARRIVAL OF MATERIAL AT A PQINT IN A ROLLING MILL Filed June 6, 1960 5 Sheets-Sheet 5 01m HARLEY IA/{'06 Ah/ l-s WWZZwW My; I

United States Patent lid M1563 BETECTIQN on THE ARRHVAL 0F MATEREAL AT A lt'JlNT EN A ROLLHNG MILL .l'ohn Harley and .lairoh Zaweis, Pretoria, Transvaal, Re-

public of South Africa, assignors to South African Iron and Steel industrial Corporation Limited, Pretoria, Transvaal, Republic at death Africa, a corporation of South Africa Filed June 6, 19st), Ser. No. 34,165 (Claims priority, application Republic of South Africa June 15, 1959 19 Claims. (Cl. fill-3) Up to the present, indication of the arrival of a rod, or other material at a point in continuous rolling mills was invariably accomplished by means of photo-electric cells, either by interrupting a light source or by utilizing the emission of light of the glowing rod, strip or the like itself. In continuous rolling mills rolling hot material, e.g. strip or rods, this method has never been reliable since heat, steam, water, metallic dust, grease and dirt, which are present in or engendered in such mills, constitute an unfavourable environment for relatively fragile photo tubes, whether of the solid state or of the vacuum type.

It is an object of the invention to provide a new method and means for detecting the arrival of a rod or other material at a given point in a rolling mill system and/or for an exactly timed operation on said rod or material. In particular it is an object to provide such means and methods which give dependable results where photoelectric cells cannot be successfully or reliably applied.

Some of the advantages of the proposed new system, which it is our object to obtain are the following:

An adequate resistance to the high temperatures arising in hot mills, complete independence from optical conditions, in particular the transparency of the medium in which the detection takes place and high resistance against mechanical impacts. In addition the new system must function reliably even if two batches of material follow each other up very closely.

The new method and means are applicable for the following purposes:

(1) The automatic cropping of distorted heads which, in existing rolling mills, is often accomplished manually at a suitable stage of the rolling process.

(2) The control of collapsible guides between stands permitting the formation of a free loop.

(3) Automatic scrap alarm and cutting in the event of cobble.

Further objects, advantages and applications of the invention will become apparent from the following description:

A method in accordance with the invention for detecting the arrival of a rod or other material at a point in rolling mills and/or for a timed operation on said rod or other material comprises coupling the two parts of the apparatus to form part of an electrical circuit, passing the electrically conductive element between the first part of the apparatus and the second part thereby completing the circuit and changing the current flow condition by initiating a flow of current in the circuit, continuing to move the electrically conductive element until it leaves the first part of the apparatus thereby breaking the circuit for changing the current flow condition by terminating the flow of current, and detecting at least one of the changes of condition of current flow.

Similarly the breaking of the loop indicates the time at which the rear end of the rod or other material being rolled leaves the preceding stand or stands in relation to the said time.

The expression electromagnetic induction effect when used herein includes electromagnetic induction or changes in an electromagnetic induction condition.

Preferably, the closed electrical loop comprises the rod or other material being rolled, two rolling stands and.

ground, or alternatively, the material being rolled, the rolls which make contact with the material and the couplings to the rolls and the common gear box driving the two consecutive stands.

In the said method, in accordance with the invention, the material being rolled preferably passes through or in proximity to a magnetic core or torroid provided with a suitable number of windings set up between two mill stands.

We have observed that the electrical loops closed by the materials being rolled often contain a considerable amount of electric noise due to, for example, the stray magnetic fields from the driving mill motors. Accordingly, a preferred method in accordance with the invention further comprises detecting the noise voltage when present in an adequate degree induced on the windings of the magnetic core through or in proximity to which the material passes.

Other alternative methods are possible, in particular if no usable noise is present in the loop. One of these methods comprises injecting a signal into the loop. This may be accomplished by providing a separate core in relation to the loop which is connected to a signal source. An alternative method comprises inducing a signal from another electrical loop or an antenna.

Alternatively a source of electromotive force may be permanently connected across a Winding round the core, the changes of impedance of this winding serving as the detected or actuating signals. According to the same principle oscillations may be set up in the winding, the change of impedance stopping the oscillations thus providing the signal. The latter method of quenching oscillations has the advantage of avoiding, for all practical purposes, any danger of pitting occurring in the gears and bearings as a result of too high a current flowing through the external surface. The choice of frequency in the above-mentioned methods depends on the physical size of the loop, the resistivity of the rod or the like and the dimensions of the driving shaft, gear box etc.

The method in its various forms may be applied to any of the purposes listed in the introduction to this specification.

Because the front of the rod tends to split open during rolling it is necessary to cut a length of from one to two feet off the front ends. This is done by means of a shear set up following on one of the intermediate stands. It is, therefore, necessary to predict the time of arrival of the rod at the shear, which in turn depends on the mill speed. Another factor which has to be borne in mind is the time lag between the operation of the electro-pneumatic solenoid valve or equivalent actuating means of the shear and the active movement of the shearing mechanism. According to one method in accordance with the invention, the time interval between the detection or actuating signal and the operation of the cropping shear is controlled by integrating the voltage from a tachometer generator coupled to the mill from the moment of the detector signal and triggering the shear mechanism when the total integrated voltage reaches a predetermined level as determined by a voltage discriminator.

Equipment, in accordance with the invention for detesting the arrival of a rod or other material being rolled at a point in rolling mills and/ or for a timed operation on said rod or other material, in which mills the rod or other material being rolled or a part thereof forms a closed electerial giving rise to an electromagnetic induction effect when the said electrical loop is closed, and means for detecting said induction elfect and/or means influenced by the said induction effect for the timed actuation of a device operating on said rod or other material.

Preferred components of the rolling mill with which the rod or the like forms a closed electrical loop have been hereinbefore indicated.

The detector or actuating means further comprise an amplifier circuit for suitably amplifying the detected signal. The detector or actuating means normally comprise an annular core with a suitable number of torroidal windings and adapted for the passage of the rod or other material being rolled through the said core.

According to one embodiment, the installation is adapted to detect the noise currents arising in the loop comprising the said material being rolled as soon as this loop is closed.

An alternative embodiment comprises a second core or another loop or antenna or equivalent for injecting a signal into the loop comprising the material being rolled, the first-mentioned core or equivalent detecting means serving to detect the closing of the loop in the same manner as previously described.

In accordance with a further alternative embodiment, a signal transmitter is permanently connected across a winding around the detecting core, the amplifying circuit being adapted to amplify the effect of the change of the impedance of this winding as a result of the closing or opening of the loop. The signal transmitter may be an oscillator.

The invention and the manner in which it may be put into practice will be further described by way of example with reference to the accompanying drawings without thereby limiting the scope of the invention.

In the drawings:

FIG. 1 is an overall diagrammatic view of an installation in accordance with the invention;

FIG. 2 is a fragmentary diagrammatic view of an installation, illustrating another embodiment of the invention;

FIG. 3 is a fragmentary diagrammatic view of an installation, illustrating a further embodiment of the invention;

FIG. 4 represents a view in perspective, partly broken away of a detail showing one embodiment of the detecting core in accordance with the invention;

FIG. 5 is a graph showing the responses of the amplifier (excluding input transformer);

FIG. 6 is a wiring diagram of an amplifying circuit for amplifying the signal currents induced onto the secondary winding of the detector core;

FIG. 7 represents an integrator, discriminator and flipflop circuit which may be used in conjunction with the amplifier and detecting means for the automatic actuation of a cropping shear; and

FIG. 8 represents a power supply circuit for stabilizing the various voltages which affect the accuracy of the installation when used as an automatic cropping control.

Referring to FIG. 1 the device is operated by a motor M. The material being rolled in the form of a rod 1 has closed an electric loop composed of the rod 1, the rollers 2 and 2' of the mill stands a and c, the coupling 3, and gear boxes 4 and 4' and the main gear box 5 driving the two consecutive stands a and c. The rod 1 passes through a detector core 6 with windings 7. An electrical current flowing around the loop induces a current in winding '7 the induced current providing a signal which indicates completion of the loop. The signal induced in winding 7 is amplified and serves to switch on a pneumatic actuator 8 after a time delay which causes the head 9 of the rod 1 to be cutoff by the disc shear 10.

According to the one embodiment the noise currents in the loop 1, 2, 3, 4, 5, 4', 3, 2', induce corresponding currents in winding 7 of the core 6. These induced noise currents then serve as the signal which is amplified.

As can be seen from FIG. 1, the loop is completed when rod 1 bridges stands a and c. It will be appreciated that as rod 1 travels along the mill, the loop will be interrupted when the trailing end of rod 1 leaves the rearward stand a. The interruption of the loop will terminate the current induced in winding 7, and the termination of the current can be utilized to provide a signal indicating the departure of the trailing end of rod 1 from rearward stand a.

In case the noise currents are insufiicient or for some reason unsuitable for detection, a current may be specially induced in the loop as shown in FIG. 2. Core 6a through which rod 1 passes, is provided with winding 7a connected to a source of current 11. Current flowing through winding 7a causes current to be induced in the closed loop. The current flowing through the loop produces a signal ind winding 7 of core 6 by direct electromagnetic induction.

Instead of producing the signal by direct electromagnetic induction, the arrangement of FIG. 3 may be used. Winding 7b on cure 612 forms part of the circuit of oscillator 12 which may be of any suitable design and which may be arranged to oscillate when the loop is open. Upon closure of the loop, the impedance of winding 7!) is changed electromagnetically. The impedance change, in turn, causes the oscillations to cease, thus providing the signal. Alternatively, the oscillator may be quiescent when the loop is open, the impedance change upon closure of the loop, causing oscillation. An output can be obtained from terminals 13. The impedance change effect will be understood clearly by a person skilled in the art.

The detector shown in FIG. 4 is of the type employed in the case of the first-mentioned embodiment. It consists of a circular core 6 having a square cross section and is wound torroidally with approximately turns of ceramic insulated wire 7. This is encased in asbestos 8 and in turn enclosed in a steel sheath 9, which has a circumferential opening 10 in it on the inside of the coil, as otherwise it would constitute a short-circuited secondary turn. The noise voltage which appears across the primary is of the order of 0.5 millivolt and the impedance looking into the winding is of the order of 10 ohms. On the outside of the case are fitted four lugs which locate the core centrally on the exit guide of stand 4 as seen in FIG. 2.

In order to present a sharp and consistant signal from a noise source it is necessary to amplify the signal from the detector, rectify it, and then differentiate it. Moreover, to eliminate spurious noise, such as power frequency hum, or very high frequency transients, the amplifier is broadly tuned around a frequency of 1 kilocycle. The response of the amplifier is shown in FIG. 5. This response is achieved by means of a parallel T resistance capacitance network, and by selecting suitable by-pass and shunt capacities, as shown in FIG. 6. The gain per stage is approximately 27 and the overall voltage gain of the amplifier at 1 kc. is 20,000. Full wave rectification is accomplished by means of the one-to-one output transformer, the secondary of which is centre tapped, and two RSZZA silicon diodes. The rectifying signal is smoothed by means of the 0.05 microfarad condenser and fed into a cathode follower. The output from the cathode follower is differentiated by means of a 0.1 microfarad capacitor. The RS22A diode is here used for rapid resetting. The most direct way of determining the time interval between the closing of the loop and the actuation of the cropping shear is to integrate the voltage from a tachometer generator coupled to mill motor M, being proportional to the speed of the mill and the integrated voltage accordingly being proportional to the distance covered by the material after reaching stand c. The commencing time of integration is obtained from the detector. To the voltage being integrated, must now be added a voltage proportional to the distance that would have been r" :3 covered by the rod in the fixed time, between the operation of the solenoids controlling the movement of the shear mechanism and the actual movement of the shear mechanism, since it may be assumed that the mill speed is constant over this time interval. This added voltage is proportional to the actual velocity of the mill. When the total voltage reaches a predetermined level, as determined by a voltage discriminator, it triggers the flying shear mechanism.

Mathematically, let the velocity of the rod be given by v(t). If D is the desired distance from mill stand at which the electrical loop is closed at the time t=0, to the tip of the rod which is to be cut, and T is the operating time of the shear arising from mechanical inertia, then where T is the time after i=0 when the shear should be triggered, v, is the velocity of the rod at the instant of triggering, and dt represents the differential of time.

From the tachometer generator, voltage proportional to the velocity of the rod are obtained and in particular the voltages V -=bv(t) and Vt bVt where b is a constant.

Hence the triggering voltage is given by T! V all V.dz+V,]

Examination of Equation 4 suggests that the required voltage may be obtained by driving a series RC circuit from a constant current generator, and measuring the voltage across the circuit which is given by V=CL idH-iR (5) where i is a current proportional to the voltage of the tachometer generator. The circuit is shown in FIG. 7 (V3). Here C is the 4 at". integrating capacitance, R is the 1.5 megohm integrating resistance, R is the inertia control represented by a 100 kilo-ohm potentiometer, V is the tachometer voltage, and V is the discriminator voltage set by the 10 kilo-ohm length adjust potentiometer.

The discriminator (V4) in FIG. 7 is a cathode-coupled multi-vibrator, the multi-vibrations being held oil by biasing the left-hand half of the tube negatively, beyond cut-off. The cathode potential is thus fixed by the potential of the grid of the right-hand half of the tube, which functions in this case simply as a cathode-follower.

As the voltage across the capacitor rises to the point where the left-hand triode starts conducting, its plate voltage drops, cutting oil the right-hand triode, and due to :the positive feed-back cathode coupling, the Whole system flips over, and a large negative impulse is fed out from the common cathodes. This is transmited to V5.

V5 is connected as a bi-stable cathode-coupled flipfiop. A negative-pulse fed onto the right-hand grid (pin 2 serves to operate the 2,000 ohm relay 13, and a negative-pulse fed onto the left-hand grid (pin 7) serves to release it.

As described earlier, the output from the amplifier is rectified and difierentiated, resulting in a negative pulse on the receipt of a noise signal, i.e., when the loop is completed as a result of the rod arriving at stand c.

When the right-hand grid of the flip-flop double triode (V5, pin 2) goes negative, the voltage across this triode rises, making the grid of the left-hand triode (pin '7) go positive. Due to the positive feedback cathode coupling, the system flips over in much the same way as the discriminator circuit, and the 2,000 ohm relay is operated. This relay in operating, opens the ohm loop across the 4 ,uf. integrating condensor, at the same time transmitting a ground out to terminal '7'. This grounding results in the operation of the cropping mechanism in such a way that the system prepares to cut the rod. The actual cutting is not efiected until this earth is removed.

fter the integrating time which is dependent on the tachometer voltage, and the inertia setting, as described, the discriminator flips over, and the right-hand grid of the flip-flop tube (pin 7) is made negative, and it in turn flips back to its original condition, thereby releasing relay 13. The earth from the output terminal '7 is thus removed, and cropping takes place.

All voltages are stabilised by means of a constant volt age power transformer (see FIG. 8). This is accomplished by resonating the high tension secondary of the transformer, and allowing a leakage flux path between the primary and the secondary. The high tension secondary is also rectified and smoothed to provide the DO supplies for the amplifier and control circuits. Full wave rectification to provide both the negative and posi* tive supplies has here been employed.

Further voltage tubes have been introduced (VR 150) to insure a very constant voltage almost entirely free from mains fluctuations. For the discriminator bias, still another voltage regulating tube (type 85A2) has been connected, since this voltage must be extremely constant in order that consecutive cuts shall be reproducible.

Soothing of both the positive and negative supplies has been conventionally accomplished with capacitive input with a series chokes.

What I claim:

1. A method of determining the location of an electrically conductive metal element traveling along a rolling mill between two spaced rolling stands of the mill, comprising the steps of coupling the two rolling stands to form part of an electrical circuit, passing the metal ele ment from the first rolling stand to the second rolling stand for completing the circuit and initiating a flow of current in the circuit, and detecting the change in con dition of the current flow from no current flow to current flow.

2. A method of determining the location of an electrically conductive metal element traveling along a rolling mill between two spaced rolling stands of the mill, comprising the steps of coupling the two rolling stands to form part of an electrical circuit, passing the metal element between the first rolling stand and the second rolling stand with a flow of current in the circuit which is made complete by said metal element, continuing to move the metal element until it leaves the first rolling stand thereby breaking the circuit and terminating the current flow in the circuit, and detecting the change in condition of the current flow from current flow to no current flow.

3. A method of determining the location of an electri cally conductive element traveling along an apparatus between two of a plurality of parts of the apparatus which at least convey the element, comprising the steps of coupling the two parts or the apparatus to form partof an electrical circuit, passing the electrically conductive element between the first part of the apparatus and the second part thereby completing the circuit and changing the current flow condition by initiating a flow of current in the circuit, continuing to move the electrically conductive element until it leaves the first part of the apparatus thereby breaking the circuit for changing the current flow condition by terminating the flow of current, and detecting at least one of the changes of condition of current flow.

4. A method of determining the location of an electrically conductive metal element traveling along a rolling mill between two spaced rolling stands of the mill, comprising the steps of 'coupling the two rolling stands to form a part of an electricalcircuit, passing the metal element between the first rolling stand and the second I rolling stand thereby completing the circuit for changing the current flow condition by initiating a flow of current in the circuit, continuing to move the metal element until it leaves the first rolling stand of the two rolling stands thereby breaking the circuit for changing the current flow condition by terminating the flow of current in the circuit, and detecting at least one of the changes of condition of current flow.

5. A method as claimed in claim 4 in which the step of detecting the change of condition of the current flow comprises causing the change in flow of current to produce an electro-magnetic induction effect, and converting the electromagnetic induction elTect into a signal.

6. A method as claimed in claim 5, in which the signal is produced directly by electro-magnetic induction.

7. A method as claimed in claim 5, in which the signal is produced by causing the electromagnetic induction effect to change an impedance in an electrical circuit, and causing the impedance change to produce the signal.

8. A method as claimed in claim 4 in which current which is caused to flow in the circuit is a noise current, and the step of detecting the change of condition of the current flow comprises causing the change in the flow of noise current to produce an electro-magnetic induction effect, and converting the electro-magnetic induction effect into a signal.

9. A method as claimed in claim 4 and the step of inducing a current in the circuit when it is completed, and in which the step of detecting the change of condition of the current flow comprises causing the change in the flow of the induced current to produce an electro-magnetic induction effect, and converting the electro-magnetic induction effect into a signal.

10. A method as claimed in claim 4 and the step of initiating an operation on said metal element by using detection of the change in condition of the circuit.

11. A method as claimed in claim in which the step of initiating the operation is delayed for a period of time after the detection of the change in condition.

12. Apparatus for controlling the operation of a rolling mill on material, comprising detector means having at least a portion thereof located between a pair of points spaced apart along the mill and in proximity to the path of travel of a heated, electrically conductive, metal element passing along the mill, the detector means having signal producing means and sensing means coupled thereto for sensing an electro-magnetic induction effect created by a change in the metal element from no current fiow to current flow on completion of a closed electrical loop through the rolling mill from the first to the second of a pair of points when the element bridges the pair of points or from current flow to no current flow on breaking of the closed loop when the trailing end of the element departs from the first point, operating means for performing an operation on the element, and control means coupled between said detector means and said operating means for initiaing operation of the operating means in response to a signal from the detector means after an interval of time from receipt of the signal.

13. Apparatus as claimed in claim 12, in which the sensing means includes an annular core through which the element can pass and a winding wound around the core.

14. Apparatus as claimed in claim 12, in which the op erating means comprises shearing means for severing the element when it is in a predetermined position,

15. Apparatus as claimed in claim 12, in which the control means is means sensitive to the speed of travel of the element.

16. Apparatus as claimed in claim 15, in which the control means includes a tachometer generator rotatably coupled to a rotary part of the mill, integrator means coupled to said tachometer generator for commencing integration of the voltage output from the tachometer generator upon receipt of the signal from the detector means, and discriminator means coupled to said integrator means for triggering operation of the operating means when the integrated voltage reaches a predetermined value.

17. Apparatus for controlling the operation of a rolling mill on material, comprising detector means having at least portion thereof located between a pair of points spaced apart along the mill and in proximity to the path of travel of a heated, electrically conductive, metal element passing along the mill, the detector means having signal producing means and sensing means coupled thereto for sensing an electro-magnetic induction effect created by a change in the metal element from no current flow to current flow on completionof a closed electrical loop through the rolling mill from the first to thesecond of a pair of points when the element bridges the pair of points, shearing means for severing the element down line of the forward mill stand, and control means sensitive to the speed of travel of the element and coupled between said detecting means and said shearing means for triggering operation of the shearing means in response to a signal from the detector means after an interval of time from receipt of the signal.

18. Apparatus as claimed in claim 17, in which the detector means includes an annular core through which the element can pass and a winding wound around the core.

19. Apparatus as claimed in claim 17, in which the control means includes a tachometer generator rotatably coupled to a rotary part of the mill, integrator means coupled to said tachometer generator for commencing integration of the voltage output from the tachometer generator upon receipt of the signal from the detector means, and discriminator means coupled to said integrator means for triggering operation of the shearing means when the integrated voltage reaches a predetermined value.

References Cited in the file of this patent UNITED STATES PATENTS 947,744 Stohr Ian. 25, 1910 2,374,652 Cohen May 1, 1945 2,387,478 Tiffany Oct. 23, 1945 2,777,519 Speakrnan Jan. 15, 1957 2,890,750 Depken June 16, 1959 3,020,788 Peters Feb. 13, 1962 

1. A METHOD OF DETERMINING THE LOCATION OF AN ELECTRICALLY CONDUCTIVE METAL ELEMENT TRAVELING ALONG A ROLLING MILL BETWEEN TWO SPACED ROLLING STANDS OF THE MILL, COMPRISING THE STEPS OF COUPLING THE TWO ROLLING STANDS TO FORM PART OF AN ELECTRICAL CIRCUIT, PASSING THE METAL ELEMENT FROM THE FIRST ROLLING STAND TO THE SECOND ROLLING STAND FOR COMPLETING THE CIRCUIT AND INITIATING A FLOW OF CURRENT IN THE CIRCUIT, AND DETECTING THE CHANGE IN CONDITION OF THE CURRENT FLOW FROM NO CURRENT FLOW TO CURRENT FLOW. 